I carry one magazine and two knives, so with the mag in the gun, I’m even. [emoji3]
That said, the first suggestion would be the Spyderco Street Bowie. It’s probably smaller than what you’re looking for in this case. It has a 5-1/8” blade. But it’s very good steel.
https://www.knifecenter.com/item/SPF...n-Street-Bowie
Maybe the Ontario SP10 would work.
https://www.knifecenter.com/item/ONS...-kraton-handle. It’s 1095 Steel that’s powder coated, so it’s going to be easy to keep sharp and should hold up. But it’s a beast from what I’ve heard.
Or maybe a good standard Ka-Bar. I prefer some of the Ontario versions without the fuller or serrations, but your friend might like to have those. This is the one I would get if I was getting this style knife.
https://www.knifecenter.com/item/ONS...Cordura-Sheath
I’m also a big fan of ESEE's big knives, but they are all more than $100.
Good luck.